The subject invention is directed to the art of ultrasound sensors and their manufacture and, more particularly, to a manufacturing method and ultrasound sensor apparatus of the type particularly adapted for use in the passenger compartments of motor vehicle.
Ultrasound sensors of the type under consideration are commonly formed to include a cup-shaped housing defining an interior space and a base upon which a piezo element is glued or otherwise attached. Vibrations of the cup-shaped bottom or base of the housing are transferred directly to the piezo element. The electrodes of the piezo element extend from the base of the cup-shaped housing to the outside via soldered or welded electrically conductive wires or lines. The cup-shaped housing is typically sealed off by means of a pourable sealing compound, such as a synthetic resin or plastic material. The electrically conductive lines extend to the outside of the ultrasound sensor through the sealing compound and serve for connection between the piezo element at the base of the housing and associated external electronics. By theses means, it is possible to evaluate the vibration behavior of the piezo element including the characteristic power curve emitted from the piezo element.
One problem with piezo sensors of the type described above, however, is the need for tension relief in the electrically conductive wires. More particularly, since the cup-shaped housing member is sealed off by a pourable sealing compound, the electrically conductive lines extending from the piezo element to the outside of the cup-shaped housing become fixed in space within the housing by mechanical interaction with the surrounding sealing compound. The locking in place of the electric signal lines has an adverse effect on the sensitivity and accuracy in the representation of the recorded sound waves. Sensors constructed according to the above with electric signal lines extending through a sealing compound typically do not satisfy the requirements of greater sensitivity and accuracy in the representation of recorded sound waves.
It would be desirable, therefore, to provide an ultrasound sensor and method for manufacturing same which provides an improved recording of sound waves or ultrasound waves and uses a simple and cost-effective construction. It is further desirable to provide an ultrasound sensor and method for manufacturing same which converts sound waves or ultrasound waves into current response signals.
The subject invention provides an ultrasound sensor including a can-shaped housing, a sensor element arranged in the can-shaped housing, a contact device adapted for connection with the can-shaped housing, the contact device defining a central opening, and at least one electrically conductive wire connecting an electrode of the sensing element with a contact point on the contact device through the central opening.
In accordance with a further aspect of the invention, a method for manufacturing ultrasound sensors is provided and includes the steps of attaching a sensor element to the base of an outer housing, attaching a contact device onto a portion of the housing adapted to receive the contact device, and electrically connecting the contact device with the sensor element through a recess provided in the contact device using a thick-stranded electrically conductive wire.
As can be seen from the forgoing, a primary object of the invention is the provision of an improved ultrasound sensor which enables a thick flexible wire-bond connection between the electrode of a piezo element disposed within the sensor housing and a contact device. The contact device is fastened locally within the housing and includes a central aperture or opening for receiving the electrically conductive wire braid. Thereby, it is possible to assure a contact point at the piezo element which is reproducibly exactly defined in its position relative to the piezo element structure.
A further object of the invention is that the contact point beneficially has less mass in contrast to contact points in known prior art piezo elements. Accordingly, the present invention utilizes a pre-determined connection point between the conductive wire and the piezo element so that the lowest possible influence upon the vibrational behavior of the piezo element is attained. The pre-determined connection point between the electrically conductive wire and the piezo element is easily reproducible and can be employed as a contact point with high accuracy.
A further object of the invention is a reduction in the negative influence on the vibrational behavior of the piezo element due to the lower mass of the connection point relative to known contact methods practiced in the prior art ultrasound sensor technology. As a result of the thick flexible wire and connection point selection according to the invention, the lowest possible change in the mass effect, and thus in the vibrational behavior, of the piezo element is attained.
A yet further object of the invention is to ensure tension relief of the electrically conductive lines extending between the contact device and the piezo sensor element. More particularly, the ultrasound sensor construction provided in accordance with the present invention enables a device without the need of additional pourable sealing compound within the can-shaped housing. Thereby, tension relief of the electrically conductive lines extending between the piezo sensor element and the contact device is assured.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.